Electrically shielded tubular jacket



May 14, 1963 w. A. PLuMMl-:R 3,089,915

ELECTRIGALLY SHIELDED TUBULAR JACKET Filed June 2v, 195o Fl G. 4. I

INVENTOR. F G. 5. WALTER A. PLUMMER United States Patent C M 3,089,915ELECTRECALLY SHIELDED TUBULAR JACKET ti/alter A. illuminer, 3546 CrownRidge Drive, Sherman Oaks, Calif. Filed lune 27, 1960, Ser. No. 38,997 9Claims. (Cl. 174-36) This invention 'elates to tubular jacketing andmore particularly to an improved laminated tube of flexible materialfeaturing an inner layer of electrically conductive material adapted toform a continuous tubular enclosure having its opposite lateral edges inelectrical Contact throughout the length thereof and including aconductive extension from one end by Iwhich the conductive layer can begrounded.

The present application is a continuation-in-part of a related inventiondisclosed in my co-pending application for United States Letters PatentSerial No. 687,476 filed October l, 19-57, now Patent No. 2,960,561,entitled Shielded Wire Harness.

There are many electrical environments in which it is mandatory thatelectrical flux fields be confined to or excluded from a designatedzone. it has been common practice heretofore to achieve these ends byerecting an electrically conductive shield about .the zone in suchmanner as to confine the iiux fields in the particular manner requiredfor each application. The present invention is directed to an improvedjacket for these purposes formed from lightweight, compact, laminatedmaterial specially constructed for assembly into a tubular enclosure ofthe particular size required to protect the zone involved. The presentproduct is particularly suitable for enclosing cabling, instrumentationand the like equipment and comprises an elongated strip of laminatedmaterial having at least one layer of non-conductive electricallyinsulating material and a second layer of very flexible high eiiiciencyconductive material. To effect the expeditious assembly and disassemblyof this jacketing about the items to be protected the opposite lateraledges are provided with non-metallic slide fastener tapes havinginterlocking tongues and grooves .to form `an easily opened and closedseam.

rflic construction incorporates certain new and irnproved features ofthe general nature just discussed and others specially designed with aview to increasing the utility, effectiveness and convenience of use ofthe closely related shielding jacket disclosed and claimed in `the aboveidentified co-pending application. For example, in the identified prior`disclosure a preferred conductive layer consists of metal foil bondedto the main body layer of thin flexible plastic material. To assure acontinuous conductive path circumferentially of the foil layer the freeedge of the guard iap of that construction was overturned upon itself:and suitably so secured. Since this guard flap was arranged to underliethe jacket seam with its overturned metallic edge positioned in directcontact with the juxtaposed lateral edge of the conductive layer,assurance was provided of the desired continuous conductive path betweenthe two longitudinal edges of the metallic layer. However, in practicein environments wherein the jacketing was subjected to rough handlingand to repeated severe flexing it was found that the metallic layertended to rupture and 'to separate from the non-conductive layerparticularly at the overturned reverse bend portion along the free edgeof the guard flap. Such failure of the metal foil interfered `seriouslywith tlie electrical shielding effectiveness of the construction. Anadditional disadvantage of the prior construction resides in the factthat lacking was a convenient and satisfactory means for grounding theconductive layer. Additionally, it was found that the metal foil layerwas not as effective an electric shield at certain frequencies as wasdesired.

3,089,915A Patented May 14, 1963 The foregoing and other shortcomingsare avoided by the present invention wherein the conductive layer isprovided by a very soft highly flexible fabric material of highstrength. Preferably this fabric comprises a nonconductive filament coreof nylon or the like high strength filament having a continuous metallicfilm exterior coating. Threads of such material are utilized to providea very closely woven fabric exhibiting unusual strength while being sosoft and liexible `as to belie the presence of a metallic lrn. Thisfabric has the feel, softness and flexibility of a soft cotton fabricyet has high conductivity and an unusual-ly high efliciency as anelectrical shield for high frequency flux fields. This conductive layeris easily laminated to a plastic main body layer in a variety of waysbut most readily and easily by stitching along its opposite lateraledges. Owing to its softness and flexibility this conductive layer isreadily overturned about the free edge of the guard flap one or moretimes and stitched or otherwise secured in place.

Anotherimportant feature of the construction is the inclusion of acontinuous flexible electrical conductor lengthwise of the jacket andpreferably along the free edge of the guard flap and secured to thelatter along with the fabric layer as by stitching. Fine wire braidingmakes an excellent conductor and its opposite ends may extend beyondAthe jacketing `and be encased with an `insulating cover up to itsterminal fitting.

Accordingly, it is a primary object of the present invention to providean improved electrically shielded tubular jacket having novel featuresnot heretofore available.

Another object of .the invention is the provision of an elongatedflexible vwalled jacket adapted to be readily assembled into tubularform and featuring a flexible electrical conductor intimately associatedwith the conductive layer of the jacket and extending from one endthereof.

Another object of the invention is the provision of an electricallyshielded jacket having an outer layer of iiexible plastic materialformed with interlocking tongue and groove seam means along its edgesand featuring an interior conductive layer of soft fabric materialhaving one edge thereof folded over to embrace the edge of the jacketguard Iflap and adapted to lie in intimate Contact with the juxtaposedother edge of the conductive layer to form a continuous tubularelectrical shield.

These and other more specific objects will appear upon reading thefollowing specification and claims and upon considering in connectiontherewith the attached drawing to 'which they relate.

Referring now to the drawing in which a preferred embodiment of theinvention is illustrated.

FGURE 1 is a fragmentary View in perspective of a short length of ashielding jacket incorporating the features of the present invention;

FIGURE 2 is a perspective view of a length of the jacketing assembledinto =a tube;

FIGURE 3 is a fragmentary enlarged cross-sectional view `taken alongline 3 3 on FIGURE 2;

FIGURE 4 is a fragmentary view on enlarged scale taken along line 44 onFGURE l; and

FGURE 5 is a cross-sectional view similar to FIG- URE 3 but showing aVariant in the mode of securing the flexible grounding wire to theiiexible shielding layer.

Referring first to FIGURES l to 4 there is shown a preferred embodimentof `an electrically shielded jacket according `to the present inventionand designated generally it). Although various non-conductive flexiblema terials may be used to form the main body strip 11, thin sheetthermo-plastic material offers many advantages. Polyethylenes and vinylsare particularly suitable as are numerous other thermo-plastics. Suchmaterials are inexpensive, easily processed, readily available, veryliexible, have excellent electrical insulating properties, resistabrasion and attack by many materials and are impervious to liuids.

Secured along the opposite lateral edges of the main body strip 11 aresuitable seam forming means, as for example, the extruded slide fastenertapes 12 and 13. Each is provided along its free edge with suitablecomplementally shaped interlocking tongue and groove means with thegrooves of each facing in opposite directions in the manner illustratedin FIGURE 1, wherein they are adapted to form a seam 14 extendinglongitudinally of the jacket. The details of these slide fastener tapesare well known and Iare disclosed more fully in the above mentionedco-pending application. As is made clear by the drawing, tape 13 ispreferably spaced appreciably inwardly from one edge of body strip 411to provide a guard flap 15 suiciently wide to bridge the seam whenclosed for purposes to be explained more fully presently.

Co-extensive with the main body strip 11 of the jacket is van interiorlayer 17 of conductive material, the material here shown comprising veryclosely woven fabric, the individual threads of which have anon-conductive filament core 13 (FIGURE 4) of nylon or the like Ihighstrength lament. The exterior of this core is coated with a continuousfilm of metal 19 such as annealed aluminum. This provides a veryflexible continuous conductive layer having superior shieldingcharacteristics particularly for high frequency iiux fields. Layer 17may be suitably laminated against the interior surface of body layer 11as by bonding or by stitching Ztl'. As here shown, stitching Ztl*extends along spaced apart junction areas, as for example, along thejuxtaposed lateral edges of layers 11 and 17. To be noted from FIGURES land 3 is the fact that the left-hand edge of the conductive fabric isoverturned to embrace the free edge of guard flap 15. Thereafter, aflexible conductor 22 of fine wire braid Iis pressed fiat against theexterior fold 23 of the fabric and is then stitched securely to the edgeof the guard ap by stitching 20.

The ends of braid 22 preferably project a suitable distance beyond theend of the jacket proper and are encased in insulation 24 after the tipend of the wire braid is provided with a convenient terminal tab 25 bywhich the same may be attached to a ground connection. Supplementalreinforcing may be employed to anchor the braid to the end edge of theguard flap. Such anchorage may comprise a pair of grommets 26 extendingthrough the conductor and the underlying portion of the guard flap andserving to reinforce the assembly and to prevent stitching 20 `frombeing pulled loose.

It is pointed out that braid 22 preferably extends the full length ofthe guard liap and therebeyond `for an aph propriate length. In certainapplications it will be desirable to cut the jacketing to length and tomake provision for an additional length of braid 22. This can beaccomplished by cutting a length of jacketing longer than is needed.Thereafter, several inches of the excess tubing is cut away leaving acorresponding length of the braid exposed beyond the jacket end.Grommets 26 are then inserted to anchor the parts together and theexposed end of the braid is covered with insulation 24 and secured to aterminal tab 25. In this manner it will be understood that the jacketingmay be manufactured in a continuous length and shipped coiled flat tothe place of use. There the jacketing is cut to length in the mannerjust described with at least one end of the grounding bra-id 22extending beyond one end of each cut length of the jacketing.

It is further pointed out that in certain applications of the jacketing`it is desirable to provide for venting the interior space to theatmosphere. For this purpose it will be understood that the outernon-conducting layer 11 is provided at intervals with vent holes 28,these preferably being of small diameter and spaced as necessarylengthwise of the jacketing. Desirably, however, vent holes 28 extendthrough only the non-conducting layer and not through conductive layer17. The interstices between the closely Woven threads of this fabricsuffice to pass air for venting purposes without, however, breaking thecontinuity of the continuous shielding provided thereby.

A second preferred embodiment of the invention shown in FIGURE 5comprises the same constituents and is constructed in the same mannerdiscussed above in connection with FIGURES 1 to 4. For this reason itwill be understood that the same reference characters have been employedas in the first embodiment and are distinguished therefrom by theapplication of a prime. The principal feature of difference in the twoembodiments resides in the fact that flexible conductor cable 22' iswrapped within the fabric layer of conductive material so as to beenclosed by the fabric before being secured by stitching 20' to the freeedge of guard ap 15. This expedient prevents the harsher and stiffermaterial constituting conductor 22 from abrading and cutting through themuch softer material of conductive layer 17'. In all other respects itWill be understood that the second embodiment conforms with thedescribed details of the lirst embodiment.

In use, it will be understood that the jacket is wrapped aboutconductors or equipment to be enclosed and shielded. Usually the jacketis tailored or manufactured to size fitting the parts to be enclosedrather snugly. The interlocking tongues and grooves constituting seam14, 14 are then pressed together in the usual manner to complete theassembly, care being exercised that guard fiap 15 underlies and bridgesthe seam with the free conductive edge thereof overlapping and inintimate contact with the juxtaposed lateral edge of the conductivelayer.

If desired, the interitting tongue and groove portions of the seam areprovided with a suitable sealant prior to being closed and serving toybond the same permanently closed. In other applications, however, therewill be need for gaining access to the interior of the jacketing inwhich event the sealant is not employed. After the jacket has beeninstalled the free end of the ground lead braid 22 is connected to asuitable ground in known manner to the end that charges tending toaccumulate on conductive layer 17 may be quickly bled away.

While the particular electrically shielded tubular jacket herein shownand disclosed in detail is fully capable of attaining the objects andproviding the advantages hereinbefore stated, it is to be understoodthat it is merely illustrative of the presently preferred embodiments ofthe invention and that no limitations are intended to the details ofconstruction or design herein shown other than as defined in theappended claims.

I claim:

1. An elongated tubular jacket for electrical conductors and the like tobe shielded with respect to electrical ux fields, said jacket comprisinga long narrow thinwalled main body of liexible pliant .electricallynon-conductive material having secured along its opposite lateral edgesinterlocking tongue and groove seam means for holding said jacketassembled about electrical conductors, one lateral edge of said mainbody projecting throughout its length laterally beyond said seam meansto provide a guard flap adapted to underlie and bridge said seam in theclosed assembled position of the seam, an interior layer of compactlywoven soft-textured fabric of electrically conductive materialsubstantially coextensive in area with said non-conductive main body andhaving one lateral edge thereof embracing the edge and both opposedsurface areas of the free edge portion of said guard ap, and meanssecuring said conductive fabric loosely assembled against one surface ofsaid non-conductive main body and about the free edge portion of saidguard flap to provide a continuous tubular shield of conductive materialin the assembled condition of said jacket seam.

:2. An electrically shielded tubular jacket as defined in claim 1characterized in that said electrically conductive 5 fabric is securedto said non-Conductive main body by stitching.

3. An electrically shielded tubular jacket as defined in claim 1characterized in that said conductive and nonconductive layers thereofare held laminated loosely together by stitching extending along thelateral longitudinal edges of said main body.

4. An electrically shielded tubular jacket as defined in claim 1characterized in that the individual threads of said soft-texturedconductive fabric have a high strength textile core coated with atenacious lm of metal.

5. An electrically shielded tubular jacket as dened in claim 1characterized in the provision of a thin flexible high strengthelectrical conductor secured to the free edge of said guard flap and inintimate contact with said conductive fabric and by which said fabric isadapted to -be grounded.

6. An electrically shielded jacket as dened in claim 5 wherein saidfabric and said high strength conductor are held assembled to the freeedge of said guard flap by a common row of stitching.

7. An electrically shielded jacket as defined in claim 1 characterizedin the provision of small perforations forming vent openings atintervals along said non-conductive main body which vent openings arecovered on the interior side of the jacket by said layer of conductivefabric.

8. An elongated tubular jacket for electrical conductors and the like tobe protected with respect to the ingress or egress of electrical -uxfields, said jacket having a laminated main body strip including anexterior layer of thin flexible non-conductive plastic material securedalong spaced apart junction areas to an interior layer of substantiallyequally ilexible conductive fabric material, plastic slide fastener seammeans secured to said main body strip in a. manner providing a guardflap along one edge adapted to underlie and bridge the interior side ofsaid seam in the closed condition of the seam, and electricallyconductive material embracing the free edge of said guard flap andincluding a long Wide but thin exible electrical conductor separate fromsaid fabric layer extending beyond the end of said jacket, saidlast-named means being electrically joined to the conductive layer ofsaid laminated main body and being positioned to lie in direct contactwith the opposite lateral edge of said conductive layer in the assembledcondition of said seam to provide a continuous tubular shield throughoutthe length of said jacket and including a grounding terminal portionextending beyond one end of the jacket for convenience in forming aground connection for said jacke 9. A tubular jacket as dened in claim 8wherein said ilexible grounding electrical conductor comprises a stripof fine ilexible wire having an insulating covering enclosing only theend portion thereof extending beyond said jacket.

References Cited in the tile of this patent UNITED STATES PATENTS2,536,003 Du Pre Dec. 26, 1950 2,585,054 Stachura Feb. l2, 19522,848,390 Whitehurst et al. Aug. 19, 1958 2,960,561 Plummer Nov. 15,1960

1. AN ELONGATED TUBULAR JACKET FOR ELECTRICAL CONDUCTORS AND THE LIKE TOBE SHIELDED WITH RESPECT TO ELECTRICAL FLUX FIELDS, SAID JACKETCOMPRISING A LONG NARROW THINWALLED MAIN BODY OF FLEXIBLE PLIANTELECTRICALLY NON-CONDUCTIVE MATERIAL HAVING SECURED ALONG ITS OPPOSITELATERAL EDGES INTERLOCKING TONGUE AND GROOVE SEAM MEANS FOR HOLDING SAIDJACKET ASSEMBLED ABOUT ELECTRICAL CONDUCTORS, ONE LATERAL EDGE OF SAIDMAIN BODY PROJECTING THROUGHOUT ITS LENGTH LATERALLY BEYOND SAID SEAMMEANS TO PROVIDE A GUARD FLAP ADAPTED TO UNDERLIE AND BRIDGE SAID SEAMIN THE CLOSED ASSEMBLED POSITION OF THE SEAM, AN INTERIOR LAYER OFCOMPACTLY WOVEN SOFT-TEXTURED FABRIC OF ELECTRICALLY CONDUCTIVE MATERIALSUBSTANTIALLY COEXTENSIVE IN AREA WITH SAID NON-CONDUCTIVE MAIN BODY ANDHAVING ONE LATERAL EDGE THEREOF EMBRACING THE EDGE AND BOTH OPPOSEDSURFACE AREAS OF THE FREE EDGE PORTION OF SAID GUARD GLAP, AND MEANSSECURING SAID CONDUCTIVE FABRIC LOOSELY ASSEMBLED AGAINST ONE SURFACE OFSAID NON-CONDUCTIVE MAIN BODY AND ABOUT THE FREE EDGE PORTION OF SAIDGUARD FLAP TO PROVIDE A CONTINUOUS TUBULAR SHIELD OF CONDUCTIVE MATERIALIN THE ASSEMBLED CONDITION OF SAID JACKET SEAM.